<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>流光按钮</title>
    <style>
        body{
            margin: 0;
            padding: 0;
            background-color: #000;
        }
        .position{
            position: absolute;
            top: 50%;
            left: 50%;
        }
        a{
           transform: translate(-50%,50%);
           width: 200px;
           height: 60px;
           text-align: center;
           line-height: 60px;
           color: #fff;
           font-size: 24px;
           text-decoration: none;
           font-family: sans-serif;
           box-sizing: border-box;
           background: linear-gradient(90deg,#03a9f4,#f441a5,#ffeb3b,#03a9f4);
           border-radius: 30px;
           z-index: 1;
           background-size: 400%;
        }
        @keyframes animate{
            from{
                background-position: 0%;
            }
            to{
                background-position: 400%;
            }
        }
        a::before{
            content: '';
            position: absolute;
            inset: -5px;
            z-index: -1;
            background: linear-gradient(90deg,#03a9f4,#f441a5,#ffeb3b,#03a9f4);
            background-size: 400%;
            border-radius: 40px;
            opacity: 0;
        }
        a:hover::before{
            filter: blur(20px);
            opacity: 1;
            animation: animate 8s linear infinite;
        }
    </style>
</head>
<body>
    <a class="position" href="#">BUTTON</a>
</body>
</html>